Plastic has taken the place of other materials in a variety of industries. In the packaging industry, plastic has replaced glass to minimize breakage, reduce weight, and reduce energy consumed in manufacturing and transport. In other industries, plastic has replaced metal to minimize corrosion, reduce weight, and provide color-in-bulk products.
Attracting consumers to purchase individually-sized or family-sized containers includes branding and trade dress. Among the elements of valuable trade dress is the color of the container. Moreover, such color may need to co-exist with translucency, transparency, or other special effects for the bottle.
Existing liquid color concentrate technology uses carrier systems that are based on surfactants, oils and/or plasticizers. These products are often incompatible with many polymers resulting in loss of physical properties, processing problems like screw slippage. Many of the existing carriers affect the clarity of optically clear polymers, such as polycarbonate (PC), polymethyl methacrylate (PMMA), styrene-acrylonitrile (SAN). Therefore, liquid color concentrates are not used with these plastic resins.
Also existing color concentrate carriers have limited heat stability and not used to color polymers, such as PC which is processed at about 600° F. (315° C.).
Currently, pellet-based concentrates, and pre-colored resins are used. But such uses also present problems. Pellet-based concentrates for tint applications have be used at high dilution or “letdown” ratios to achieve good color distribution. Pre-colored resins are expensive to manufacture and warehouse. Such resins also undergo two heat histories (initial compounding and subsequent molding), which can be detrimental to some polymers.